diff --git a/src/nqrduck_spectrometer/pulseparameters.py b/src/nqrduck_spectrometer/pulseparameters.py
index e081848..e4dcdf0 100644
--- a/src/nqrduck_spectrometer/pulseparameters.py
+++ b/src/nqrduck_spectrometer/pulseparameters.py
@@ -1,3 +1,4 @@
+import logging
 import numpy as np
 import sympy
 from pathlib import Path
@@ -6,6 +7,8 @@ from nqrduck.contrib.mplwidget import MplWidget
 from nqrduck.helpers.signalprocessing import SignalProcessing as sp
 from .base_spectrometer_model import BaseSpectrometerModel
 
+logger = logging.getLogger(__name__)
+
 class Function():
     name: str
     parameters : list
@@ -31,9 +34,13 @@ class Function():
     def evaluate(self, pulse_length: float) -> np.ndarray:
         """Evaluates the function for the given pulse length."""
         n = int(pulse_length / self.resolution)
-        t = np.linspace(-np.pi, np.pi, n)
+        t = np.linspace(self.start_x, self.end_x, n)
         x = sympy.symbols("x")
 
+        # If the expression is a string, convert it to a sympy expression
+        if isinstance(self.expr, str):
+            self.expr = sympy.sympify(self.expr)
+
         found_variables = dict()
         # Create a dictionary of the parameters and their values
         for parameter in self.parameters:
@@ -69,6 +76,7 @@ class Function():
     def add_parameter(self, parameter : "Function.Parameter"):
         self.parameters.append(parameter)
 
+
     class Parameter:
         def __init__(self, name : str, symbol : str, value : float) -> None:
             self.name = name
@@ -76,6 +84,10 @@ class Function():
             self.value = value
             self.default = value
 
+        def set_value(self, value : float):
+            self.value = value
+            logger.debug("Parameter %s set to %s", self.name, self.value)
+
 class RectFunction(Function):
     name = "Rectangular"
     def __init__(self) -> None:
@@ -88,6 +100,8 @@ class SincFunction(Function):
         expr = sympy.sympify("sin(x * l)/ (x * l)")
         super().__init__(expr)
         self.add_parameter(Function.Parameter("Scale Factor", "l", 2))
+        self.start_x = -np.pi
+        self.end_x = np.pi
 
 class GaussianFunction(Function):
     name = "Gaussian"